The present invention relates to a CRT (cathode ray tube), and more particularly to a CRT having improved springs that are used to secure a shadow mask assembly to a CRT panel.
A conventional color CRT has a shadow mask having circular or slit-shaped apertures for color selection purposes. In the fabrication of the CRT, a frame is welded to clips, which clips are usually bimetallic in order to maintain registration between the mask and a phosphor pattern on a panel with temperature changes. The shadow mask is then welded to the frame, resulting in a shadow mask assembly. A spacer is then placed behind the CRT panel and then the assembly is placed behind the spacer. Springs, having stud receiving holes, are then placed on studs that are disposed on the four sides of the panel and the springs welded to the clips. The spacer is then removed. It will be seen that various manufacturing tolerances are involved, in particular, mask-to-frame, frame-to-clip, and clip-to-spring tolerances. All of the tolerances involved allow a large tolerance error build up to occur.
The panel then goes through various steps of matrixing, screening, and aluminizing, which steps involve about five insertions and four removals of the shadow mask assembly from the panel. The insertion is done by a machine called a "mask inserter" such as shown in U.S. Pat. No. 4,451,243 and under common assignment herewith, and the removal is done by a "mask remover". However, due to said tolerance errors, accurate location of the stud holes may not take place, and therefore improper insertion (less than all four springs receiving a stud) occurs resulting in misregistration of the shadow mask with respect to the panel. The improper insertion is detected and the CRT production line is stopped. Thus a loss of production is the result.